Dual layer fusion bond epoxy coating for continuous sucker rod

ABSTRACT

Embodiments of the present disclosure generally relate to apparatus and methods for manufacturing continuous sucker rods with protective coatings. One embodiment provides a coating system including a first drive station disposed on a first end of a coating line, a second drive station disposed on a second end of the coating line to move a continuous sucker rod along the coating line from the first drive station to the second drive station, a heater disposed along the coating line, and a first coating station disposed along the coating line.

BACKGROUND Field

Embodiments of the present disclosure generally relate to continuous sucker rods having one or more protective coatings, and apparatus and methods for applying one or more coatings on continuous sucker rods.

Description of the Related Art

In oil and gas wells, a “drive string” connects the pump, located down hole, to the drive system, located at the surface. Sucker rods are generally used in a drive string. A conventional drive string typically includes a sequence of conventional sucker rods with connecting mechanisms at each end of each conventional sucker rod which permit end-to-end interconnection of adjacent rods. Conventional sucker rods are elongated steel rods, 20 feet to 30 feet in length. Each interconnection point between two successive conventional sucker rods is a source of potential weakness and excess wear on the adjacent tubing and casing.

Alternatively, a drive string may include one continuous sucker rod to avoid weakness caused by interconnection points between conventional sucker rods. A continuous sucker rod is a unitary rod, consisting of one elongated continuous piece of steel. Continuous sucker rod is typically produced and stored for sale on large transport reels. These transport reels have a maximum diameter of about 19 to 20 feet and the diameter may be as small as 9-10 feet. A full reel can carry continuous sucker rod with lengths of over 6,000 feet depending on the diameter of the rod. However, the length of a drive string can vary from anywhere from as little as 500 feet to as much as 10,000 feet or more, depending on the depth of the well and desired location of the pump down hole.

Drive strings in oil and gas wells are exposed to increasingly aggressive corrosive conditions for many domestic and international producers. Corrosive condition may include fluids consist of an oil & water mix that can have varying concentrations or partial pressures of H₂S or CO₂ alone or in combination. The presence of chloride ions is also common, which act to accelerate or enhance the corrosive nature of the other constituents. Additionally, the well fluid carries along a lot of sand and slit particles causing wear, which tends to expose continuously more bare metal to the corrosive condition of the well fluid. Protecting drive strings from corrosion is challenging due to the natural of the material used, typically carbon or alloyed steel to obtained flexibility for handling and carbon or alloyed steel are not designed for corrosion resistance. Protecting continuous sucker rods from corrosion is even more challenging than other drive strings because continuous contact with the tubing combined with the movement up and down in reciprocating or rotational in progressing cavity pumping applications prevents the build-up of a protective coating to guard against corrosion. Additionally, the form of corrosion protection must be adaptable to a continuous rod manufacturing operation.

Therefore, there is a need for continuous sucker rod products with greater inherent resistance to corrosive environments, and apparatus and methods for manufacturing corrosive resistance continuous sucker rods.

SUMMARY

Embodiments of the present disclosure generally relate to apparatus and methods for manufacturing continuous sucker rods with protective coatings.

One embodiment provides a coating system including a first drive station disposed on a first end of a coating line, a second drive station disposed on a second end of the coating line to move a continuous sucker rod along the coating line from the first drive station to the second drive station, a heater disposed along the coating line, and a first coating station disposed along the coating line.

Another embodiment provides a method for coating a continuous sucker rod. The method includes moving the continuous sucker rod at a substantially constant speed a long a coating line, and while moving the continuous sucker rod, heating the moving continuous sucker rod at a first location of the coating line, and applying a first coating on an outer surface of the moving continuous sucker rod at a second location of the coating line.

Another embodiment provides a continuous sucker rod. The continuous sucker rod includes a body, a first coating applied on an outer surface of the body, wherein the first coating comprises a thermosetting polymer and has a first thickness, and a second coating applied on the second coating, wherein the second coating comprise a thermosetting polymer and has a second thickness. The first thickness is smaller than the second thickness.

Another embodiment provides a mobile servicing unit for repairing a coated continuous sucker rod. The mobile servicing unit comprises a trailer, a heater disposed on the trailer, a grit blaster disposed on the trailer, and a coating station disposed on the trailer.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features of the present disclosure can be understood in detail, a more particular description of the various aspects, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this disclosure and are therefore not to be considered limiting of its scope, for the disclosure may admit to other equally effective embodiments.

FIG. 1 is a schematic plan view of a continuous sucker rod coating system according to one embodiment of the present disclosure.

FIG. 2 is a flow chart of a method for applying protective coatings on a continuous sucker rod according to one embodiment of the present disclosure.

FIG. 3 is a schematic sectional view of a continuous sucker rod having protective coatings according to one embodiment of the present disclosure.

FIG. 4 is a schematic plan view of a mobile service unit according to one embodiment of the present disclosure.

FIGS. 5A-5C schematically illustrate a support structure according to one embodiment of the disclosure.

FIGS. 6A-6C schematically illustrate a support structure according to one embodiment of the disclosure.

FIGS. 7A-7B schematically illustrate a coating station according to one embodiment of the present disclosure.

To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements disclosed in one embodiment may be beneficially utilized on other embodiments without specific recitation. The drawings referred to here should not be understood as being drawn to scale unless specifically noted. Also, the drawings are often simplified and details or components omitted for clarity of presentation and explanation. The drawings and discussion serve to explain principles discussed below, where like designations denote like elements.

DETAILED DESCRIPTION

In the following description, numerous specific details are set forth to provide a more thorough understanding of the present disclosure. However, it will be apparent to one of skill in the art that the present disclosure may be practiced without one or more of these specific details. In other instances, well-known features have not been described in order to avoid obscuring the present disclosure.

Embodiments of the present disclosure generally relate to apparatus and methods for manufacturing continuous sucker rods with protective coatings. In one embodiment, one or more coatings may be applied to a continuous sucker rod while moving the continuous sucker rod continuously. In one embodiment, the one or more coatings may include two coatings applied by powder spray.

FIG. 1 is a schematic plan view of a continuous sucker rod coating system 100 according to one embodiment of the present disclosure. The continuous sucker rod coating system 100 may be used to apply one or more protective coatings on a continuous sucker rod.

The continuous sucker rod coating system 100 may include two drive stations 120, 122 configured to move a continuous sucker rod through a coating line 101. Various devices/equipment may positioned along the coating line 101 so that a continuous sucker rod may coated with protective coatings as the continuous sucker rod passes through the coating line 101. In one embodiment, the coating line 101 may be substantially linear. The drive stations 120, 122 may be disposed at opposing ends of the coating line 101. In one embodiment, each drive station 120, 122 may include a transport reel capable of winding and/or unwinding a continuous sucker rod thereon. Each drive station 120, 122 may include guides and safety devices arranged to support a transport reel. The drive stations 120, 122 may be set up with a crane or other suitable lifting devices.

In one embodiment, the drive station 120 may include a supply reel having a continuous sucker rod to be coated wound thereon, and the drive station 122 may include a take up reel configured to wind the continuous sucker rod thereon after coating. During coating process, the take up reel of the drive station 122 may rotate to move a continuous sucker rod from the drive station 120 to the drive station 122 at a desirable speed. In one embodiment, the desirable speed may be a substantially constant speed.

In one embodiment, one or more support structures 102, such as rollers and support frames, may be disposed along the coating line to reduce bucking or other deformations as the continuous sucker rod travels through the coating line 101.

The continuous sucker rod coating system 100 may further include a central control station 105. The central control station 105 may be configured to operate and coordinate various devices/stations in the continuous sucker rod coating system 100. For example, the central control station 105 may be control the steering of the drive station 120 and/or drive station 122 to control the speed of the continuous sucker rod travelling along the coating line 101. In one embodiment, the central control station 105 may control the drive stations 120, 122 to move a continuous sucker rod in a substantially constant linear speed along the coating line 101. The central control station 105 may be configured to monitor the coating process, acquire and record operation data, and perform analysis of the operation.

In one embodiment, the continuous sucker rod coating system 100 may include a weld station 110 configured to weld a string element on an end of a continuous sucker rod to be coated. By welding string elements to ends of the continuous sucker rod, the entire length of the continuous sucker rod may move through the coating line 101 and get coated. In one embodiment, the weld station 110 may be disposed adjacent the drive station 120 to weld a string element on a leading end of a continuous sucker rod before the continuous sucker rod is exposed to other devices. A string element may be a scrap piece of continuous rod of the same or different size. Similarly, the weld station 110 may also weld a string element to a tail end of the continuous sucker rod so that the tail end may be coated.

Additionally, the weld station 110 allows the continuous sucker rod coating system 100 to manufacture and coat a sucker rod of various designs. For example, a continuous sucker rod may be a tapered string with accessories to match the strength requirements, for example for reciprocating applications. The tapered string may be made up of varies pieces of strings of different cross sections with the biggest cross section on the top of the string and the smallest cross section towards the bottom of the string. The accessories could be a short piece of big cross section string at the very bottom end of the tapered string to improve on the string behavior/characteristics on the forced downward stroke. All these pieces may be welded together in the weld station 110. The weld area may then be cleaned and coated in the subsequent stations of the continuous sucker rod coating system 100.

The continuous sucker rod coating system 100 may a surface preparation station 130 configured to prepare and clean an outer surface of the continuous sucker rod travelling therethrough for coating. The surface preparation station 130 may be disposed downstream of the weld station 110.

In one embodiment, the surface preparation station 130 may include a wheelabrator 132 or similar device configured to achieve a predefined surface roughness on the continuous sucker rod. The wheelabrator 132 may perform a continuous grit blasting operation on the passing continuous sucker rod. In one embodiment, the wheelabrator 132 may include a grit recovery and dust control vacuum. In one embodiment, the surface preparation station 130 may further include an air blaster 134 for dust removal. The surface preparation station 130 may further include a washer 136 configured to wash the continuous sucker rod with a solvent to remove organic contamination. In one embodiment, an air stream blower 138 may be disposed downstream the washer 136. An air stream from the air stream blower 138 may be used to thoroughly dry the continuous sucker rod after solvent washing in the washer 136. In one embodiment, the wheelabrator 132, the air blaster 134, the washer 136 and the air stream blower 138 may be disposed sequentially along the coating line 101.

The continuous sucker rod coating system 100 further includes a heater 140 for heating the continuous sucker rod to a desirable temperature as the continuous sucker rod travels through the heater 140. The heater 140 may be disposed downstream of the surface preparation station 130. In one embodiment, the heater 140 may be an induction heating system with a heating coil. During operation, a continuous sucker rod to be coated travels through the heating coil. The heating coil may be customized to accommodate a specific continuous sucker rod to heat the specific continuous sucker rod to a desired temperature as the continuous sucker rod travels therethrough. In one embodiment, the heater 140 may be used to heat the continuous sucker rod all the way through to a target temperature.

The continuous sucker rod coating system 100 may include a first coating station 150 disposed downstream from the heater 140. A second coating station 160 may be disposed downstream from the first coating station 150. The first and second coating stations 150 are configured to apply one or more protective coatings on the continuous sucker rod. In one embodiment, the one or more protective coatings may be formed from thermosetting polymers, such as fusion bond epoxies. In one embodiment, the one or more protective coatings include an inner layer and an outer layer. The inner layer may be selected from coatings having good adhesion to the base material of the continuous sucker rod, thus providing a high level of protection to fluid ingress. The outer layer may be selected from coating materials capable of providing protection for the inner layer against damages sustained during service and operation.

In one embodiment, the first coating station 150 may include a plurality of coating/spray guns configured to spray a powder for forming the first coating. The plurality of coating/spray guns in the first coating station 150 may be stationary and set to apply a predetermined amount of powder onto the continuous sucker rod travelling at the constant speed. Alternatively, the first coating station 150 may use other methods, such as dip coating, to apply the first coating.

The second coating station 160 may include a plurality of coating/spray guns configured to spray a powder for forming the second coating. The plurality of coating/spray guns in the second coating station 160 may be stationary and set to apply a predetermined amount of powder onto the continuous sucker rod travelling at the constant speed. Alternatively, the second coating station 160 may use other methods, such as dip coating, to apply the first coating.

A distance 145 between the first coating station 150 and the heater 140 may be arranged so that the surface of temperature of the continuous sucker rod is ideal for applying a first coating when the continuous sucker rod arrives at the first coating station 150 at a constant speed.

A distance 155 between the first coating station 150 and the second coating station 160 may be arranged so that the surface of temperature of the continuous sucker rod is ideal for applying a second coating when the continuous sucker rod arrives at the second coating station 160 at the constant speed. In one embodiment, the time needed for the continuous sucker rod to travel through the distance 155 also allows the first coating on the continuous sucker rod to adhere properly to the outer surface of the continuous sucker rod and to solidify enough for applying the second coating.

In one embodiment, a distance 153 between the first coating station 150 and the next support structure 102 downstream to the first coating station 150 is arranged so that the first coating can solidify to a condition that the forces exerted from the support structure 102 to the travelling continuous sucker rod are not damaging or deforming the first coating layer. Similarly, a distance 163 between the second coating station 160 and the next support structure 102 downstream to the second coating station 160 is arranged so that the first coating can solidify to a condition that the forces exerted from the support structure 102 to the travelling continuous sucker rod are not damaging or deforming the second coating layer.

In one embodiment, a cooling distance 165 may follow the second coating station 160 to allow the first and second coatings to cure. In one embodiment, a cooling station 170 may be disposed downstream to the second coating station 160. The cooling station 170 may be used to actively cool the continuous sucker rod and the coatings applied thereon, therefore, accelerate curing and solidification of the coatings.

In one embodiment, an inspection station 180 may be disposed adjacent the drive station 122. The inspection station 180 may operate to check for flaws and marks on the applied coatings as the continuous sucker rod passes through before being windup on the take up reel at the drive station 122. The inspection station 180 may be used to ensure that the coatings are continuous and free of flaws. In one embodiment, the inspection station 180 may send data and/or inspection results to the central control station 105. The central control station 105 may record the data for later use, such as a repair operation.

It should be noted, the central control station 105 may be connected to any of the surface preparation station 130, the heater 140, the first coating station 150, the second coating station 160, the cooling station 170, the inspection station 180, the drive stations 120, 122, and any of the support structures 102, to operate the stations, to monitor the process parameters, and/or to record processing data. In one embodiment, analysis may be conducted in the central control station 105 to provide quality assurance and to use a base for trouble shooting.

In one embodiment, the continuous sucker rod coating system 100 may include a coating repair station 190. The coating repair station 190 may be disposed along the coating line 101 and configured to perform local repairs after a coating process. The repair station 190 may be disposed at any point along the coating line 101 even though in FIG. 1 the repair station 190 is shown to be upstream to the surface preparation station 130.

The repair station 190 may be an enclosed booth including devices for manually performing surface preparation, such as grit blasting, solvent washing, and air drying, and powder coating a stretch of flowed continuous sucker rod. In one embodiment, the repair station 190 may include a grit blasting booth 192, a mobile induction heater 194, and a powder spray booth 196. The grit blasting booth 192 may include a grit recovery and dust control vacuum. The powder spray booth 196 may include climatized powder storage and a dust control vacuum. The mobile induction heater 194 may be disposed between the grit blasting booth 192 and the powder spray booth 196 to heat a stretch of continuous sucker rod after cleaning and prior to applying the powder coating. Alternatively, a stretch of continuous sucker rod may be driven to the heater 140 that is set in a repair heating cycle and heated by the heater 140 while the continuous sucker rod remains stationary. After heated to a desired temperature, the stretch of continuous sucker rod may be driven back to the repair station 190 where new coatings may be applied.

In one embodiment, the coated continuous sucker rod may be driven back from the drive station 122 to the drive station 120 so that stretches of the continuous sucker rod with flaws or markings may be positioned within the repair station for repairs. In one embodiment, the coated continuous sucker rod may be driven back according to the recorded data from the inspection station 190. Alternatively, the coated continuous sucker rod may be run through the continuous sucker road coating system 100 at a later time for a manual inspection and a repair may be performed upon detection of flaws and markings in the repair station 190.

In one embodiment, at least one of the surface preparation station 130, the first coating station 150, the second coating station 160, and the repair station 190 may be equipped with a suitable directed airflow and filtration system to accommodate the workplace and environmental regulation requirements.

In one embodiment, the continuous sucker rod coating system 100 may be arranged adjacent to a continuous sucker rod manufacturing system. A continuous sucker rod may be coated after coming off a manufacturing system. In one embodiment, a separate repairing line may be used with the continuous sucker rod coating system 100. A coated continuous sucker rod may be transferred to the separate repairing line to have defects repaired. In another embodiment, components of the continuous sucker rod coating system 100 may be arranged in the line of a continuous sucker rod manufacturing system so that a continuous sucker rod may be manufactured and coated in a single run.

FIG. 2 is a flow chart of a method 200 for applying protective coatings on a continuous sucker rod according to one embodiment of the present disclosure. In method 200, dual coating layers are applied to a continuous sucker rod in a continuous process while the continuous sucker rod moves through a coating system. The method 200 may be performed using a coating system, such as the continuous sucker rod coating system 100 described above.

In box 210 of the method 200, a string leader element may be attached to at least one end of a continuous sucker rod to be coated. The string leader elements allow the entire length of the continuous sucker rod to be coated. In one embodiment, the string leader elements may be attached to the continuous sucker rod by welding, such as by welding in the weld station 110 of the continuous sucker rod coating system 100.

In box 220 of the method 200, the continuous sucker rod to be coated may be moved at a substantially constant speed along a coating line from a loading station to an unloading station. In one embodiment, the loading station may be the drive station 120 of the continuous sucker rod coating system 100 and the unloading station may be drive station 122 of the continuous sucker rod coating system 100. The substantially constant speed may be determined by the distances between a heating station, and coating stations positioned along the coating line.

In box 230 of the method 200, an outer surface of the continuous sucker rod may be prepared for coating as the continuous sucker rod passes through a surface preparation station positioned between the loading station and the unloading station. In one embodiment, surface preparation may include grit blasting an outer surface of the continuous sucker rod to a predefined surface roughness. In one embodiment, the outer surface of the continuous sucker rod may have a surface roughness between about 0.0015 inches to about 0.0045 inches in the Ra (arithmetic average) roughness scale. Surface preparation may further include air blasting for dust removal following grit blasting. Surface preparation may further include washing the blasted surface with a solvent to remove any organic contaminants. In one embodiment, washing the outer surface may be performed by spraying the continuous sucker rod with or passing the continuous sucker rod through a solvent. Suitable solvents may include water, such as water filtered by a reverse osmosis method, a slight acidic solution, a slight alkaline solution, methyl ethyl ketone (MEK), n-propyl bromide (EnSolv), trichloroethylene (Vextrel X-P10), or combinations thereof. In one embodiment, the solvent may be a slight acidic solution having a PH value between about PH5 to about PH7. In one embodiment, the solvent may be a slight alkaline solution having a PH value between about PH7 to about PH9. The washing may be followed by drying with an air stream. In one embodiment, the surface preparation may be performed by passing the continuous sucker rod through a grit blasting station, such as the grit blasting station 132, an air blaster, such as the air blaster 134, a washer, such as the washer 136, and an air stream, such as the air stream 138.

In box 240 of the method 200, the continuous sucker rod may be heated to a desired temperature as the continuous sucker rod passes through a heater positioned between the loading station and the unloading station, such as the heater 140 of the continuous sucker rod coating system 100. In one embodiment, the continuous sucker rod may be heated by inductively as the continuous sucker rod passes through a coil of the heater 140. The continuous sucker rod may be heated to a temperature so that when the heated portion of the sucker rod arrives at the coating station, the surface temperature of the continuous sucker rod is suitable for the coating process. In one embodiment, the continuous sucker rod may be heated through to a temperature between about 245 degrees Celsius and about 250 degrees Celsius.

In box 250 of the method 200, a first layer of coating may be applied to the continuous sucker rod as the continuous sucker rod passes a first coating station positioned between the loading station and the unloading station, such as the first coating station 150. In one embodiment, the first coating may be a corrosion inhibition and corrosion protection layer. In one embodiment, the first coating may be fusion bond epoxy layer applied by powder coating. In one embodiment, the fusion bond epoxy include about 6% of 4,4-isopropylidene diphenol, about 4-15% expoxy novolac, and less than 1.0% of 2-methylinmidazole. In one embodiment, the first coating may have a thickness between about 0.002 inches to about 0.005 inches. The first coating may smooth the roughened outer surface of the continuous sucker rod to some degree. However, dimples may remain on the roughened outer surface after the first coating. In one embodiment, the first coating may be applied by spray coating while the continuous sucker rod having a surface temperature between about 235 degrees Celsius and about 239 degrees Celsius. The thickness of the first coating may be varied by varying the speed of the continuous sucker rod, and/or adjust the flow rate of the spray guns. Alternatively, the first coating may be applied by other method, such as by dipping. Alternatively, the first coating may be formed from other suitable material, such as suitable fusion bond epoxy powders by DuPont.

In box 255 of the method 200, the first layer of coating is solidified by traveling at a predetermined distance out of the first coating station. The first layer of coating may be solidified for a second coating.

In box 260 of the method 200, a second layer of coating may be applied to the continuous sucker rod as the continuous sucker rod passes a second coating station positioned between the loading station and the unloading station, such as the second coating station 160. In one embodiment, the second coating may be a friction and abrasion reduction layer. The second coating reduces friction with other material and reduces wear/abrasion caused by well fluids which may contain a substantial amount of silica crystals (sand) and silt, thus providing protection to the first coating. In one embodiment, the second coating may be fusion bond epoxy layer applied by powder coating. In one embodiment, the fusion bond epoxy include about 13-26% of calcium silicate, about 6% of 4,4-isopropylidene diphenol, and less than 1.0% of 2-methylinmidazole. In one embodiment, the second coating may have a thickness between about 0.015 inches to about 0.02 inches. In one embodiment, the thickness of the second coating may be selected so that the dimples on the roughened outer surface of the continuous sucker rod are filled to achieve a smooth surface on the continuous sucker rod. In one embodiment, the second coating may be applied by spray coating while the continuous sucker rod having a surface temperature between about 232 degrees Celsius and about 235 degrees Celsius. The thickness of the second coating may be varied by varying the speed of the continuous sucker rod, and/or adjust the flow rate of the spray guns. Alternatively, the second coating may be applied by other method, such as by dipping. Alternatively, the second coating may be formed from other suitable material, such as suitable fusion bond epoxy powder by the DuPont.

In one embodiment, the first coating and the second coating may be selected from materials that are chemically related so chemical connections form between the first and second coatings. The chemical connections improve the adhesion between the coatings thus improving protection to the continuous sucker rod.

In box 265 of the method 200, the first and second coatings are solidified and cured as the continuous sucker rod travels at a predetermined distance out of the second coating station. During curing and solidifying, the coatings are untouched to enable continuous and flawless coating over the continuous sucker rod.

In box 270 of the method 200, the continuous sucker rod may be optionally cooled as the sucker rod passes a cooling station positioned between the loading station and the unloading station, such as the cooling station 170.

In box 280 of the method 200, the coatings are inspected as the sucker rod passes an inspection station positioned between the loading station and the unloading station, such as the inspection station 180. In one embodiment, the inspection station 180 may send locations or other information of flaws or markings on the coatings to a central control station, such as the central control station 105.

In box 290, the continuous sucker rod may be driven back so that locations with flows or marking may be moved to a repair station positioned between the loading station and the unloading station, such as the repair station 190. In one embodiment, the continuous sucker rod may be driven back according to the recorded data in the central control station.

In box 295, the locations with flaws or markings may be repaired in the repair station. In one embodiment, repairing the flaws and markings may include surface preparation, heating, and coating. Surface preparation may include grit blasting, air blasting, solvent washing, and air dry as described with the repair station 190.

FIG. 3 is a schematic sectional view of a continuous sucker rod 300 having protective coatings according to one embodiment of the present disclosure. The continuous sucker rod 300 may be manufactured using the method 200 described above. The continuous sucker rod 300 may include a body 302 having an outer surface 304. The body 302 may have a cylindrical cross section as shown in FIG. 3. Alternatively, the body 302 may have an elliptical cross section, a semi-elliptical cross section, or any other suitable cross sections.

A first coating 310 may be formed on the outer surface 304 of the body 302. The first coating 310 may be directly applied to the outer surface 304. The outer surface 304 may be prepared to have a surface roughness between about 0.0015 inches to about 0.0045 inches in the Ra (arithmetic average) roughness scale to achieve desired adhesion between the body 302 and the first coating 310. The first coating may be a layer of thermosetting polymer. In one embodiment, the first coating 310 may function to provide corrosion inhibition and corrosion protection to the body 302. In one embodiment, the first coating may be a fusion bond epoxy layer having a thickness between about 0.002 inches to about 0.005 inches. As shown in FIG. 3, the first coating 310 may have a roughened outer surface similar to the outer surface 304. The waviness of the first coating 310 improves the adhesion between the first coating 310 and the body 302 of the continuous sucker rod.

A second coating 320 may be formed on the first coating 310. The second coating 320 may be directly applied to the first coating. In one embodiment, the second coating provides protection to the first coating by reducing friction and abrasion caused by well fluids which may contain a substantial amount of silica crystals (sand) and silt. The second coating may be a layer of thermosetting polymer. In one embodiment, the second coating may be fusion bond epoxy layer having a thickness between about 0.015 inches to about 0.02 inches. As shown in FIG. 3, the thickness of the second coating 320 smoothes out the wavy surface of the first coating 310. The smooth outer surface of the second coating 320 reduces friction coefficient therefore improving resistance against attacks from resistance media and/or wear media.

The first coating 310 and second coating 320 may be selected from suitable fusion bond epoxy powder. In one embodiment, the first coating 310 may be a fusion bond epoxy powder that is configured to directly apply to metals. In one embodiment, the first coating 310 may be BLACK BEAUTY 7-0017 DTM by DuPont. The first coating 310 may have a thickness between about 0.016 inches to about 0.040 inches. In one embodiment, the first coating 310 may have a thickness about 0.020 inches. In one embodiment, the first coating 310 may include a primer directly applied to the body 302 and a fusion bond epoxy powder applied over the primer. In one embodiment, the first coating 310 may include a primer between about 0.00075 inches to about 0.0025 inches. The first coating 310 may include a fusion epoxy layer of about 0.016 inches to about 0.040 inches applied over the primer. In one embodiment, the primer may be a Phenolic Primer 7-1808 by DuPont. Alternatively, the primer may be any suitable material.

The second coating 320 may be selected from a fusion bond epoxy powder. Suitable material for the second coating 320 may be Gold Dual 7-2504, Nap-Rock 2610, NapGard 7-2502 non-slip, NapGard 7-0017, NapGard 7-2504 Gold, NapGard 7-2675 by DuPont, or the likes. The second coating 320 may have a thickness between about 0.020 inches to about 0.055 inches.

Alternatively, the first coating and the second coating may be formed from the same material. For example, both the first coating and second coating may be a fusion bond epoxy powder.

The continuous sucker rod 300 has robust corrosion resistance to an aggressive production fluid environment because the first coating 310 and the second coating 320 provide a barrier to corrosion of the body 302, resist against mechanical damage during handling. Since the first coating 310 and the second coating 320 are a barrier only, areas of the body 302, which is made of steel, that become exposed during operation will not experience accelerated corrosion damage due to galvanic effects as happened to the prior art continuous sucker rod. Additionally, the first and second coatings are applied at a temperature that will not disrupt previously established mechanical properties of the body 302 which is made of steel. The coating material solidifies rapidly enabling a continuous application method, which is both efficient and economical.

The first coating 310 may be applied as thin as possible and economically feasible as long as a complete flaw-free continuous coating is formed around the body 302. In one embodiment, the first coating 310 may have a thickness in the range of a few thousands of an inch. For example, the first coating 310 may have a thickness between about 0.010 inch and 0.030 inch.

The second coating 320 may serve as protection for the first coating 310. Due to the low friction coefficient of the coating material to the adjacent lubricated metal, the second coating 320 also act as a mechanical interface to the rod body 302 for the mechanical handling of the rod string. In one embodiment, during the mechanical handling, the second coating 320 may be permanently deformed in a planned manner and engaged with shear strength of the coating material to transmit the holding forces along a limited length of rod. To provide protection and mechanical strength, the thickness of the second coating 320 is larger than the thickness of the first coating 310. In one embodiment, the second coating 320 is between about 3 times to about 30 times in thickness of the first coating 310. For example, the second coating 320 is between about 3 times to about 10 times in thickness of the first coating 310. In one embodiment, the second coating 320 may have a thickness between about 0.020 inches to about 0.055 inches.

The thinner first coating 310 improves the adhesion between the first coating and the body 302. The thicker second coating 320 is stronger due to the thickness, thus preventing the thinner first coating 310 and the body 302 from mechanical damage during servicing, for example, gripping, installation, removal and/or operation. It has been demonstrated that for the coating materials listed above and the deployed application equipment, it is most economical when the combined thickness of the two coatings 310 and 310 is between 0.025 in and 0.055 in. Additional to the above described features this protective layer has to maintain high flexibility in its fully cured condition to allow for several passages through the mechanical handling system which has contact surfaces with uneven smooth surface patterns,

FIG. 4 is a schematic plan view of a mobile servicing unit 400 according to one embodiment of the present disclosure. The mobile servicing unit 400 is configured to coat short stretches of a continuous sucker rod when repairing or servicing in the field.

The mobile servicing unit 400 may include an enclosed trailer 402 with a deck 404. The deck 404 may be longer than the enclosed part of the trailer 402. A non-enclosed portion 404 a of the deck 404 may be at a rear end of the trailer 402 and may be used for the installation of a field welder station 406. The mobile servicing unit 400 may include grit blasting and surface cleaning equipment 410 housed in the trailer 402. In one embodiment, the grit blasting and surface cleaning equipment 410 may be an off the shelf manual equipment. The mobile servicing unit 400 may include one or more rod manipulation/support arms 412. The rod manipulation/support arms 412 may be folded alongside the trailer 402 for travel. The mobile servicing unit 400 may include heating equipment 414 housed in the trailer 402. In one embodiment, the heating equipment 414 may include an off the shelf mobile induction heater. The mobile servicing unit 400 may include powder coating equipment 416 housed in the trailer 402. In one embodiment, the powder coating equipment 416 may be an off the shelf mobile powder coating device. A coating powder storage 418 may also be included in the trailer 402. The coating powder storage 418 may be a climate controlled container. Other tools, such as a vacuum unit 420, an air compressor 422, an electrical power unit 424, and accessories 426 may also be equipped in the mobile servicing unit 400. The vacuum unit 420 may include a filter system to contain the dust particles resulting from the various processes. The compressor 422 may be used for grit blasting. The mobile service unit 400 may further include a welding tent 428. The welding tent 428 may be used to create a controlled work space to limit the environmental footprint.

FIGS. 5A-5C schematically illustrate a support structure 502 according to one embodiment of the disclosure. The support structure 502 may be used in place of the support structure 102 in the continuous sucker rod system 100 to provide support during coating. The support structure 502 may include two frames 504, 508. An insert 506, 510 may be attached to each frame 504, 508. The frame 504, 508 may be attached to each other, for example by a hinge 512 and a pin 514. The inserts 506, 510 form a tubular passage 516 to provide support to a continuous sucker rod passing therethrough. In one embodiment, a flared portion 518 may be formed near ends of the passage 516 to direct the continuous sucker rod towards the passage 516.

The inserts 506, 510 may be formed from a material that has low friction coefficient, high resistance against wear and corrosion. In one embodiment, the inserts 506, 510 may be formed from a polymer, such as polyethylene. In one embodiment, the inserts 506, 510 are formed from an ultra high molecular weight polyethylene.

FIGS. 6A-6C schematically illustrate a support structure 602 according to one embodiment of the disclosure. The support structure 602 may be used in place of the support structure 102 in the continuous sucker rod system 100 to provide support during coating. The support structure 602 may include a frame 604, and rollers 606, 610, 612 disposed inside the frame 604. The rollers 610, 612 may be parallel to each other and the roller 606 is perpendicular to the rollers 601, 612. The rollers 606, 610, 612 form a passage 620 to support a continuous sucker rod passing therethrough. In one embodiment, a guide pin 608 may be positioned parallel to the roller 606. The guide pin 608 may be used to provide guidance to the continuous sucker rod towards the passage 620.

Each roller 606, 610, 612 may include a shaft 614 attached to the frame 604, and a cylindrical body 618 rotatably attached to shaft 614. The cylindrical body 618 is configured to contact the continuous sucker rod. The cylindrical body 618 may be formed from a material that has low friction coefficient, high resistance against wear and corrosion. In one embodiment, the cylindrical body 618 may be formed from a polymer, such as polyethylene. In one embodiment, the cylindrical body 618 is formed from an ultra high molecular weight polyethylene.

FIGS. 7A-7B schematically illustrate a coating station 900 according to one embodiment of the present disclosure. The coating station 900 may be used in place to the coating stations 150, 160 in the continuous sucker rod system 100. The coating station 900 may include a plurality of nozzles 902, 904, 906, 908 disposed along a path 901 of the continuous sucker rod 101. Each nozzle 902, 904, 906, 908 may be configured to spray a coating material towards the path 901 to apply a coating on the continuous sucker rod 101 passing through. The nozzles 902, 904, 906, 908 may be spraying guns.

The plurality of nozzles 902, 904, 906, 908 may be distributed around the path 901 at different angles to cover the entire circumference of the continuous sucker rod 101. In one embodiment, the plurality of nozzles 902, 904, 906, 908 may be evenly distributed around the path 901. In one embodiment, the plurality of nozzles 902, 904, 906, 908 may be disposed at different locations along the path 901 so that the nozzles 902, 904, 906, 908 are not spraying at one another. In the embodiment of FIGS. 7A and 7B, four nozzles are disposed at 90 degrees from one another. Alternatively, more or less nozzles may be used.

Embodiment of the present disclosure provides a coating system. The coating system includes a first drive station disposed on a first end of a coating line, a second drive station disposed on a second end of the coating line to move a continuous sucker rod along the coating line from the first drive station to the second drive station, a heater disposed along the coating line, and a first coating station disposed along the coating line.

In one or more embodiments, the first coating station is disposed downstream to the heater at a first predetermined distance so that the continuous sucker rod moving at a substantially constant speed arrives at the first coating station at a desired temperature.

In one or more embodiments, the coating system further includes a second coating station disposed along the coating line downstream to the first coating station at a second predetermined distance.

In one or more embodiments, each of the first and second coating stations comprises one or more spray guns configured to dispend a powder coating towards the continuous sucker rod passing through the corresponding coating station.

In one or more embodiments, the coating system further includes a surface preparation station along the coating line.

In one or more embodiments, the surface preparation station comprises a wheelabrator, an air blaster, and a solvent washer.

In one or more embodiments, the coating system further includes an inspection station disposed along the coating line adjacent the second drive station.

In one or more embodiments, the coating system further includes a repair station disposed along the coating line, wherein the first drive station moves the continuous sucker rod from the second drive station to the first drive station to align a stretch of the continuous sucker rod with the repair station.

In one or more embodiments, the coating system further includes a central control unit.

Another embodiment of the present disclosure provides a method for coating a continuous sucker rod. The method includes moving the continuous sucker rod at a substantially constant speed a long a coating line, and while moving the continuous sucker rod, heating the moving continuous sucker rod at a first location of the coating line, and applying a first coating on an outer surface of the moving continuous sucker rod at a second location of the coating line.

In one or more embodiments, the method further includes, while moving the continuous sucker rod, applying a second coating on the moving continuous sucker rod at a third location on the coating line, wherein the third location is downstream to the second location, and a distance between the second and third locations is selected to allow the first coating to solidify for the second coating.

In one or more embodiments, the method further includes, while moving the continuous sucker rod, preparing the outer surface of the continuous sucker rod at a fourth location along the coating line upstream to the first location.

In one or more embodiments, preparing the outer surface comprises grit blasting the outer surface, air blasting the outer surface, and washing the outer surface with a solvent.

In one or more embodiments, the method further includes, while moving the continuous sucker rod, inspecting the continuous sucker rod at a fifth location along the coating line downstream to the third location.

In one or more embodiments, the method further includes, moving the continuous sucker rod at a reverse direction along the coating line to align a stretch of the continuous sucker rod with a repair station disposed along the coating line, and repairing the stretch of the continuous sucker rod at the repair station.

In one or more embodiments, a distance between the first and second locations is selected to allow a surface temperature of the continuous sucker rod to reach a target value at the second location.

In one or more embodiments, the first coating comprises a first fusion bond epoxy, and the second coating comprises a second fusion bond epoxy.

Another embodiment provides a continuous sucker rod, comprising a body, a first coating applied on an outer surface of the body, wherein the first coating comprises a thermosetting polymer and has a first thickness, and a second coating applied on the second coating, wherein the second coating comprise a thermosetting polymer and has a second thickness, and the second thickness is bigger than the first thickness.

In one or more embodiments, the first coating is formed from a first fusion bond epoxy and the second coating is formed from a second fusion bond epoxy.

In one or more embodiments, the second thickness is between about 3 times to about 30 times the first thickness.

In one or more embodiments, the first thickness is between about 0.002 inches to about 0.005 inches.

In one or more embodiments, the second thickness is between about 0.015 inches to about 0.02 inches.

Another embodiment of the present disclosure provides a mobile servicing unit. The mobile servicing unit includes a trailer, a heater disposed on the trailer, a grit blaster disposed on the trailer, and a coating station disposed on the trailer.

While the foregoing is directed to embodiments of the present disclosure, other and further embodiments may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow. 

1. A coating system, comprising: a first drive station disposed on a first end of a coating line; a second drive station disposed on a second end of the coating line to move a continuous sucker rod along the coating line from the first drive station to the second drive station; a heater disposed along the coating line; and a first coating station disposed along the coating line.
 2. The coating system of claim 1, wherein the first coating station is disposed downstream to the heater at a first predetermined distance so that the continuous sucker rod moving at a substantially constant speed arrives at the first coating station at a desired temperature.
 3. The coating system of claim 2, further comprising: a second coating station disposed along the coating line downstream to the first coating station at a second predetermined distance.
 4. The coating system of claim 3, wherein each of the first and second coating stations comprises one or more spray guns configured to dispend a powder coating towards the continuous sucker rod passing through the corresponding coating station.
 5. The coating system of claim 1, further comprising: a surface preparation station along the coating line.
 6. The coating system of claim 5, wherein the surface preparation station comprises: a wheelabrator; an air blaster; and a solvent washer.
 7. The coating system of claim 1, further comprising an inspection station disposed along the coating line adjacent the second drive station.
 8. The coating system of claim 1, further comprising a repair station disposed along the coating line, wherein the first drive station moves the continuous sucker rod from the second drive station to the first drive station to align a stretch of the continuous sucker rod with the repair station.
 9. The coating system of claim 1, further comprising a central control unit.
 10. A method for coating a continuous sucker rod, comprising: moving the continuous sucker rod at a substantially constant speed a long a coating line; and while moving the continuous sucker rod, heating the moving continuous sucker rod at a first location of the coating line; and applying a first coating on an outer surface of the moving continuous sucker rod at a second location of the coating line.
 11. The method of claim 10, further comprising: while moving the continuous sucker rod, applying a second coating on the moving continuous sucker rod at a third location on the coating line, wherein the third location is downstream to the second location, and a distance between the second and third locations is selected to allow the first coating to solidify for the second coating.
 12. The method of claim 11, further comprising, while moving the continuous sucker rod, preparing the outer surface of the continuous sucker rod at a fourth location along the coating line upstream to the first location.
 13. The method of claim 12, wherein preparing the outer surface comprises: grit blasting the outer surface; air blasting the outer surface; and washing the outer surface with a solvent.
 14. The method of claim 12, further comprising, while moving the continuous sucker rod, inspecting the continuous sucker rod at a fifth location along the coating line downstream to the third location.
 15. The method of claim 14, further comprising: moving the continuous sucker rod at a reverse direction along the coating line to align a stretch of the continuous sucker rod with a repair station disposed along the coating line; and repairing the stretch of the continuous sucker rod at the repair station.
 16. The method of claim 10, wherein a distance between the first and second locations is selected to allow a surface temperature of the continuous sucker rod to reach a target value at the second location.
 17. The method of claim 11, wherein the first coating comprises a first fusion bond epoxy, and the second coating comprises a second fusion bond epoxy.
 18. A continuous sucker rod, comprising: a body; a first coating applied on an outer surface of the body, wherein the first coating comprises a thermosetting polymer and has a first thickness; and a second coating applied on the second coating, wherein the second coating comprise a thermosetting polymer and has a second thickness, and the second thickness is bigger than the first thickness.
 19. The continuous sucker rod of claim 18, wherein the first coating is formed from a first fusion bond epoxy and the second coating is formed from a second fusion bond epoxy.
 20. The continuous sucker rod of claim 18, wherein the second thickness is between about 3 times to about 30 times the first thickness. 